This application claims the priority benefit of U.S. provisional application Ser. No. 61/904,998, filed Nov. 15, 2013.
Mount performance is significantly affected by the amount of air trapped under a decoupler. Determining the position of the decoupler and the relative timing of the state switching of the mount increases the performance characteristics of the mount as well as the repeatability/consistency of this performance. More particularly, one of the key performance metrics of an engine mount is phase or frequency offset. The amount of phase is affected by the amount of air trapped under the decoupler, i.e., the rubber barrier between fluid and air chambers in the mount. Air under the coupler in a first state (State 1) is allowed to vent to atmosphere. In a second state (State 2), air is trapped under the decoupler because an evacuation port is closed or blocked.
In prior applications, air under the decoupler is evacuated via a vacuum system. However, in some applications, vacuum is no longer present. Air is trapped beneath the coupler when the evacuation port is closed or plugged via an electrical actuator.
It is been determined that an ideal scenario for peak phase is a condition with the decoupler bottomed out (i.e., biased toward maximum travel in a downward direction against a lower cage of an inertia track). Detection of the decoupler position is therefore desirable for optimizing mount performance.
Many technologies are available for “position sensing” but the functional requirements, short distance, sealed chamber, and/or hostile environment, for example, of a switchable mount design make these technologies undesirable or difficult to use for this application in a vehicle. It is also important to keep in mind that a decoupler moves quickly, i.e., typically at a low amplitude and high frequency. Again, position sensing technology must be capable of detecting such movement.
For example, ultrasonic sensing uses high frequency sounds waves, and can work with a solid panel in front of the sound transducer. Although ultrasonic sensing technology may be acceptable where the target is stationary or slow-moving, the decoupler environment is fast-moving and results in a poor signal/indication of the sensed position of the decoupler.
Infrared (IR) sensing needs an optically clear window between the chambers, and generally cannot detect extremely short distances. As a result, infrared sensing is not generally conducive to sensing decoupler position in this environment.
Capacitance sensing does not work well sensing through a plastic wall and/or fluid environment when the target is rubber. The volume of fluid in the mount environment is not sufficient to make capacitance sensing a viable option.
Radio frequency sensing (RF) requires too close a distance to be useful in certain environments.
One of the key performance metrics of a vibration isolation mount or engine mount is phase (frequency offset). In this specific application, the amount of phase is affected by the amount of air trapped under the decoupler (rubber barrier between fluid and air chambers). Air under the decoupler in a first state or state 1 is allowed to vent to atmosphere. In a second state or state 2, the evacuation port is blocked, trapping air under the decoupler.
In prior applications, air under the decoupler would be evacuated via a vacuum system. In this specific application, vacuum is no longer present, and air is trapped by plugging the evacuation port via an electrical actuator.
Accordingly, a need exists to address, for example, the air trapped under the decoupler in an engine mount, and the need to provide an accurate, dependable or reliable sensing arrangement that confirms the state of the decoupler.